US Senators Edward J. Markey and Elizabeth Warren are calling for increased safety measures at two area nuclear power plants after a Nuclear Regulatory Commission report found potential vulnerabilities to earthquakes.

In a letter to NRC chairwoman Allison Macfarlane on Friday, Markey and Warren asked the commission to require that Pilgrim Power Station in Plymouth and Seabrook Station in Seabrook, N.H., “implement mitigation measures against seismic risks that were previously unknown.”

Following the 2011 meltdown at Japan’s Fukushima Dai-ichi Nuclear Power Plant, which was sparked by an earthquake and tsunami, the NRC established a task force to evaluate possible vulnerabilities at US nuclear facilities and the need for enhanced regulatory oversight, according to the NRC report released Thursday.

Markey and Warren were “alarmed” by the newly evaluated seismic risks at the two area facilities, which are greater than they were originally licensed to withstand, the senators said in the letter.

NextEra Energy Seabrook Station, which runs the New Hampshire plant, said on Friday night that it will be conducting an evaluation.

“The further evaluation of Seabrook does NOT mean that safety systems, structures or components are inadequately protected against a seismic event,” said Sarah Cloutman Gebo, a spokeswoman for the company, in a statement. “Seabrook is designed and built to withstand much stronger earthquakes than ever recorded in its region, and the plant is designed to safely shut down within seconds in the unlikely event of a strong earthquake.

“This initial screening used highly conservative assumptions about highly unlikely events, comparing the existing seismic design of Seabrook to revised seismic standards. At this point we do not anticipate that any major modifications or enhancements to the plant will be needed.”

A representative for the Pilgrim plant could not be reached for comment.

The new earthquake risk evaluations had been ongoing since about 2005, NRC spokesman Scott Burnell said Friday.

The recent measurements of seismic risk outlined in the report predict “the largest shaking [that nuclear plants] will have to deal with in the next, say, 10,000 years,” he said. All central and Eastern US reactor licensees — about 60 — submitted the required hazard re-evaluations to the NRC in March, said Burnell.

The task force then made recommendations for mitigation, or risk reduction; emergency preparedness; and efficiency at NRC facilities, according to the report.

Markey and Warren asked the NRC to direct the Pilgrim and Seabrook plants “to immediately take all necessary measures to assure the safety of the reactors and those that live and work near them.”

Burnell said, however, that the plants submitted evaluations to the NRC concluding that additional precautions taken in the course of the stations’ initial construction should be sufficient to handle any of the new, predicted seismic events.